Minor issue with new H55F (1 Viewer)

[Godwin]

In assembling a new H55F and t-case I encountered unexpected assembly issues, at least nothing that I had anticipated with new transmission. First was with the pilot bearing, which was an Aisin. The clutch kit I purchased was Aisin and in checking the fitment of the pilot bearing on the input shaft I found that it would not slide on. Not wanting to turn down the tip of the input shaft on a this new transmi$$on I decided to attempt to enlarge the inner surface of the pilot bearing. That was a fail, I overdid it. So I purchased a new bearing from Toyota, and with the expectation that since this was from Toyota the bearing would fit. Again too tight and this was a Nachi. With some sand paper I turned down the tip of the input shaft a small amount until the pilot bearing would fit.

Next was installation of the t-case input gear on the transmission output shaft. This is a new Sumo gear and it would not fully seat. I flipped it over and checked for the point of interference on the shaft, which was where the dark band transitioned to light. I first suspected an issue with the Sumo gear, really this a new transmission and things ought to go together smoothly. The Sumo gear fit the old transmission without issue. I checked with the old input gear on the new transmission shaft, same interference issue. I had to also smooth down this section of the output shaft until the gear would fit.

I was not expecting these fitment issues with a new Toyota assembly, it's all together now.

 

[OSS]

I’m sure Toyota is aware of the wear issue on the splines of the transmission output shaft and TFR input gear - cuz every old one has developed a sloppy fit.
So my guess is…. Its a tight fit on purpose. Maybe they pound it on the last inch to ensure a really snug fit.

Same thought about the input shaft tip fitting inside the pilot bearing.
If I recall, 32 years ago when I installed my new H55F, the input shaft tip was a very tight fit inside the Toyota pilot bearing. I was concerned about putting too much pressure on the transmission front bearing during installation, so I believe I slightly too honed down the front lip of the tip so it would fit better inside the pilot bearing (still snug) …. but 30 years later I paid the price.

When the pilot bearing gets old after a really long time, it doesn’t spin as well and there’s significant twisting tortion at the interference fit at the input shaft tip and bearing race.
When it becomes excessive- the input shaft breaks free of the pilot bearing race — and its all downhill after that: the input shaft tip grinds itself down inside the frozen pilot bearing.

That exact thing eventually happened to my input shaft tip to the point that it couldn’t grab the bearing race anymore…but after 230,000 miles

 

[cps432]

I didn’t have any issues with fitment with mine. I didn’t use a sumo gear. I think it was the one terrain tamer sells. My pilot bearing was only two years old when I installed my 5 speed so I just reused it and had no issues with installation. It never even came out of the crankshaft. I pulled it out last week and it’s still in perfect shape.

 

[Gimme a 60]

I was pretty sure the pilot bearing is supposed to be tight. I’m literally replacing mine right now, and sure enough, it doesn’t want to fit, and I also ordered it from Toyota. However upon the comparison of the old bearing, I discovered that the old bearing too had a extremely tight fit. It’s probably just they way it is.

 

[duncanrm]

Any minor corrosion on the tip of the input shaft causes a very tight pilot bearing fit.. its not unusual to have to clean up the input shaft with a light sandpaper to get a more comfortable fit on the pilot bearing.

 

[cruisermatt]

both of those are not issues, they are supposed to be like that.

Tight = longevity

 

[cps432]

Any minor corrosion on the tip of the input shaft causes a very tight pilot bearing fit.. its not unusual to have to clean up the input shaft with a light sandpaper to get a more comfortable fit on the pilot bearing.

It’s a brand new transmission so there should be zero corrosion.

 

[Spike Strip]

It's common to take a thousandth or so off the input shaft snout with emery cloth so you get a slip-fit with new bearing/trans.

There are some threads where people have been unable to stab the trans flush, and then try to draw the trans/Bell-housing together with the bolts and end up snapping the ears of the trans. No bueno.

 

[dogfishlake]

That is interesting, if not a bit frustrating. Jim, do you suppose some heat on the "female" surface and an icing job (dry ice?) on the "male" mating surfaces would do it, or do you feel the interference is greater than that? I usually put my wheel bearing races in the freezer to help with that process. It helps, even if it is in my own head!

Thank you for sharing the experience.

 

[duncanrm]

It’s a brand new transmission so there should be zero corrosion.

There's corrosion on the transfer case gears in your photo.. it appears like there is at least.

 

[Spook50]

I’m sure Toyota is aware of the wear issue on the splines of the transmission output shaft and TFR input gear - cuz every old one has developed a sloppy fit.
So my guess is…. Its a tight fit on purpose. Maybe they pound it on the last inch to ensure a really snug fit.

Maybe freeze the shaft and heat the bearing for installation?

Like @cruisermatt said, I suspect it's designed that way deliberately.

 

[Godwin]

It's common to take a thousandth or so off the input shaft snout with emery cloth so you get a slip-fit with new bearing/trans.

There are some threads where people have been unable to stab the trans flush, and then try to draw the trans/Bell-housing together with the bolts and end up snapping the ears of the trans. No bueno.

Which is why I smoothed the tip of the input shaft.

 

[Godwin]

There's corrosion on the transfer case gears in your photo.. it appears like there is at least.

I had gotten a little orange sealant on one of the teeth and the other stuff that appears to be corrosion was a heavy grease substance that I cleaned off prior to final installation. This was new out of the box input gear with no corrosion.

 

[Godwin]

That is interesting, if not a bit frustrating. Jim, do you suppose some heat on the "female" surface and an icing job (dry ice?) on the "male" mating surfaces would do it, or do you feel the interference is greater than that? I usually put my wheel bearing races in the freezer to help with that process. It helps, even if it is in my own head!

Thank you for sharing the experience.

I thought about heating cooling of the parts for fitment I think the interference was greater. The male shaft was ca. 0.4-5 mm (IIRC) than the female bore of the gear. I tried tapping the gear on with a rubber hammer and but it could not be driven on more than a couple of mm past the spline transition on the shaft. Once I had the shaft sanded enough for the gear to slide down most of the way I still had to drive on to fully seat it.

 

[klinetime574]

I just have to add some thoughts about the pilot bearing. I replaced my pilot bearing with Aisin when I did my H55. Did I test fit it on the input shaft on the transmission before installing the transmission? No.

I’d argue, or rather, think, that the weight of the transmission being aligned with the bell housing/clutch/pilot bearing would “eliminate” any interference felt by test fitting by hand.

Do I find this tech interesting? Yes, I do. Thanks @Godwin

As for the transfer case gears…. No clue.